Gas machine



May 4, 1937. H, v. ATWELL 2,079,536

' GAS MACHINE Filed June 30, 1932 2 Sheets-Sheet 1 mpr'eaaor INVENTOR.jzar'olddflzwell ATTORNEY May 1937. H. v. ATWELL 2,079,586

GAS MACHINE Filed June 30, 1932 2 Sheets Sheet 2 ia .30 .50 a0 .90

Tcmperatare -dg r'eaj F INVENTOR Jiaroldflflzwall ATTORNEY GAS MACHINEHarold V. Atwell, Bayside,. N. Y., assignor to Standard Oil Company,Chicago, 111., a corporation of Indiana Application June 30, 1932,Serial No. 620,187

15 Claims.

This invention relates to a process and apparatus for carburetting airwith hydrocarbons, and the invention is particularly adapted forpreparing a gaseous fuel, from liquid hydrocarbons, of

predetermined fuel value per unit volume. Heretofore, it has been thepractice to gasefy liquid hydrocarbons for fuel purposes by bubblingvairthrough said liquid in order to obtain a mixture of hydrocarbon gasesand air. However, such mixtures were too rich for commercial combustionpurposes and, in order to prepare a domestic fuel, it was necessary toadd secondary air to the vaporized hydrocarbons to adjust the heatingvalue. ardous because, inadvertently, too much secondary air wasfrequently added and the resulting mixture contained air and gas inexplosive proportions.

Therefore, one of the objects of my invention s to provide an apparatusand process for. carburetting air with normally liquid hydrocarbons toproduce a gaseous fuel of constant B. t. 11. value per unit volume andeliminate the step of adding secondary air to the gas main.

Another object is to produce'a gas machine that operates withoutattendance and one that is adapted to automatically adjust itself underdifierent climatic conditions so that the carburetted gas will alwayshave a constant heat value per unit volume of gas.

Further objects and advantages of my invention will become apparent fromthe following disclosure when read in connection with the followingdrawings, in which:

Fig. 1 of the drawings shows an elevational view of the gas machinepartly in section.

The graphs in Fig. 2 show the pressures that should be maintained in thegas machine to prepare a gaseous fuel of constant heat value atdifferent temperatures. For example, the pentane curve shows thepressure in pounds per square inch absolute required for a giventemperature to give saturation of air'with pentane of a composition ofabout 13.5% pentane, corresponding to approximately 550 B.'t. u. percubic foot of mixture at atmospheric pressure. The hexane curve showsthe pressure and temperature conditions to give a saturated hexane airmixture of constant heat value.

Figure 3 is a sectional view of a portion of the apparatus showing indetail a compensating device for variable fuel volatility.

. Briefly, the gas machine comprises a storage tank for the liquidhydrocarbons, a carburetor and a means for supplying compressed air toThis practice has proved to be very haz the carburetor. The compressedair is introduced into the bottom of the carburetor and bubbled throughthe liquid hydrocarbons. A gas space is provided above the level of thecarburant to receive the air and hydrocarbon gases. By regulating thepressure above the liquid level through the introduction of the airadded to the mixture, the ratio of air and hydrocarbon vapors can beaccurately controlled. For example, at a given temperature the vaporpressure of the car-- burant will maintain a definite and constantamount of hydrocarbon vapor in the gas space above the liquidhydrocarbon. By introducing air into the carburetor, the pressure of themix-' ture of air and hydrocarbon gases will increase in proportion tothe air pressure applied and the ratio of air to hydrocarbon gases willbecome greater, Therefore, by regulating the air pressure within thecarburetor, the ratio of air andhydrocarbon gases, and consequently thefuel value of the mixture, will be controlled. Means,hereinafterexplained, are provided for maintaining a predeterminedpressure within the gas space and means are provided for adjusting theapparatus in response to temperature so that the fuel value of the gasleaving the carburetor will have a predetermined and constant value.

The carburant, or low boiling hydrocarbon, is

stored in the tank to and fed through the conduit- H and check valve l2to the carburetor i3. A

float valve [4 and float l5 command the flow of liquid hydrocarbons andmaintain a constant level of liquid hydrocarbons within the carburetor.Thecarburetor I 3 comprises a tank, or other suitable container, adaptedto withstand high pressures. A drain pipe i6 is provided on thelowermost part of the carburetor to remove the water and objectionablematerials that collect therein.

The compressed air to be mixed with the hydrocarbon vapors is deliveredto the air storage tank l9 from the compressor H, which is operated by asuitable driving means l8. sures from '75 to pounds per square inchabsolute are adequate for the operation of the carburetor, but thepressure required will depend on the nature and volatility of the fuelemployed.

Generally, pres- Any conventional means may be employed to authe flow ofair from the air storage tank to the carburetor. The check valve 2iprevents liquids from flowing back into the air system. The conduit 23provided with the pin hole orifice 25 con- 5 nects the air storage tankIS with the upper chamber 26 of the diaphragm valve 23. When thepressure within the diaphragm chamber 26 is the same as the pressurewithin the tank l9, the valve 23 will close. Therefore, a reduction ofpressure'within the diaphragm chamber 26 will cause the valve 23 to openand permit the compressed air to pass into the carburetor. The apparatusand conditions for causing pressure fluctuations within thediaphragmchamber 26 will be described hereinafter.

A line 21 communicates with the gas space 28 above the liquid level 29and the bellows 3D. The pressure variations within the carburetor l3cause the bellows 30 to expand or contract a-predetermined and constantamount, and when the bellows expand, as-a result of an increase inpressure within the gas space 28, the lower portion of the bellows movesdownwardly and causes the bi-metallic hairpin 3i to push the valveneedie 32 against the valve seat 33, thereby closing the needle valve33. As long as the pressure within the gas space of the carburetorremains at a predetermined amount, the valve 35 remains closed, that isthe valve needle 32 remains on the valve seat 33. The conduit connectsthe needle valve 34 with the diaphragm chamber 26.-

A pressure control valve 36, operated by a diaphragm in the chamber 31,regulates and controls the flow of gases from the carburetor to the gas35 main 38. A reduction of pressure in the gas main is transmitted tothe diaphragm through the line 39, thereby causin the diaphragm to openthe valve 36 and maintain a predetermined and constant lower pressurewithin the gas main independent of the pressure of the gas within thecarburetor.

In operating the gas machine, the compressor I1 is started and airpasses through the air storage tank l9, line 20, valve 23, and isbubbled through the liquid carburant. In this example, pentane will beused as the carburant, but other low boiling hydrocarbons, suchasbutane,- hexane, heptane, casinghead gasoline or mixtures of these,may be used. The air, saturated with pentane at the prevailingtemperature, collects in the gas space 28 above the liquid level 29 ofthe pentane, and the air continues to enter the carburetor until thepressure of the gas mixture within the gas space has built up to a 55pressure that gives the desired ratio of gas and air. In this particularexample, I will describe the operation of my invention at 50 F. and itwill be observed from the curve in Fig. 2 that a pressure of 43 poundsper square inch absolute will be. required in the vapor space 28 toproduce a saturated pentane-air vapor having a composition of about13.5% pentane which corresponds to approximately 550 B. t. u. per cubicfoot measured at atmospheric pressure. Therefore, when the pressurewithin the vapor space 28 has built up to 43 pounds per square inchabsolute, the bellows 30 will have expanded and closed the needle valve34. When the needle valve 34 closes, 70 the pressure within thediaphragm chamber 26 builds up to the same pressure as in the tank l9 orline 20, thereby causing the valve 23 to close and stop the flow of airto the carburetor 13. At this state of the operation, the gases withinthe carburetor. are under 43 pounds pressure per square inch absoluteand the flow of air to the carburetor has ceased.

As the gas is withdrawn from the main 38, the pressure therein isreduced and the valve 36 is then opened to permit gas to flow from thecarburetor I3 to the main 38. As the pressure within the carburetorbegins to decrease,

the bellows contract a proportional amount and open the needle valve 33and permits air to escape through said needle valve, thereby reducingthe pressure in the diaphragm chamber 26 and causing the valve 23 toopen by action of the spring mechanism which it contains, and permitmore air to bubble through the pentane in the carburetor. As long as thepressure within the vapor space 28 is below 43 pounds per square inchabsolute, the bellows 30 will be sufficiently contracted to hold theneedle valve 33 open. Consequently, the air in the diaphragm chamber 26can escape through the needle valve 33 and reduce the pressure withinsaid diaphragm chamber 26, thereby causing the valve 23 to remain open.It should be understood that the air can escape through needle valve 33faster than the air enters the chamber 26 through the orifice 25.

Throughout the description of the above operation, the temperature wasassumed to be at 50 F. at which temperature the vapor pressure of thepentane remained constant, giving a gas of constant fuel value. Wherewide variations intemperature occur as between winter and summer andbetween day and night, I have found it necessary to employ means forcompensating for lowered fuel vapor pressure at low temperatures andvice versa. For this purpose I may employ various thermally responsivedevices and in the drawings, Fig. 1, I have shown a bimetallic coil orhairpin 3i for this purpose. This hairpin passes through the U-shapedconduit 40 that projects into the liquid within the carburetor providinga sensitive temperature shield for the bi-metallic hairpin. When thetemperature of the liquid within the carburetor is increased, forexample, to F., the volatility or vapor pressure of the liquid alsoincreases. and in order to maintain the desired ratio of air and pentanein'the space 28 to give a gas mixture of constant fuel value, it isnecessary to compress more air into this space. The increase intemperature causes the bi-metallic hairpin to contract and open theneedle valve 34, which in turn permits compressed air to enter the lowerpart of the carburetor until the pressure of the gases Within the gasspace has increased to a predetermined amount and caused the bellows toexpand sulficiently to close the valve 34. It is apparent that thehigher temperatures cause the bi-metallic hairpin to contract, that is,causing the ends of the hairpin that are connected to the bellows 30 andvalve needle 32 respectively to come closer together, thereby making itnecessary for the bellows 30 to expand to a greater 'extent before itcan push the needle valve against the valve seat 33 and stop the flow ofair to the carburetor. From the=curve in Figure 2, it will be observedthat at a temperature of 55 F., the pressure within the gas space 28should be maintained at about 49 pounds per square inch absolute inorder to produce an airpentane mixture which has a heat value ofapproximately 550 B. t. u.s per cubic foot at substantially atmosphericpressure.-

When the temperature of the liquid in the carburetor is decreased, forexample to 40 F., the

volatility of the liquid therein decreases accordingly and in order tomaintain the desired ratio of air and pentane in the vapor space 28above to give a gas mixture of constant fuel value, it is necessary toreduce the amount of air added to the carburetor. Consequently, apressure of about 34 pounds per square inch absolute must be maintainedin the space above the liquid level lnorder to produce an air-pentanemixture which has a heating value of 550 B. t. u. per cubic foot atsubstantially atmospheric pressure. The decrease in temperature causesthe bi-metallic hairpin to expand, thereby making it necessary for thebellows to contract to a greater extent than in the case of highertemperatures, before the contraction of the bellows will open the needlevalve 34.

It should be understood that the temperature changes come about slowlyand the bi-metallic needle adjusts itself to each increment oftemperature change. The thermostatic element or bi-metallic hairpincomprises two strips of metals having widely different coeflicients ofexpansion, for example, brass and steel, silver and nickel, copper andnickel. The longest strip of metal. or the one on the outside,designated a should have a higher coefficient of expansion than thestrip of metal designated b. Other thermostatic devices may be usedinstead of the embodiment herein described. For example, the bimetallicthermostatic element described in U. S. Patent 1,813,122 may beconnected between the bellows 30 and the valve needle 32. Also if thegas machine herein described is maintained at substantially constanttemperaturaitwill not be necessary to employ the aid of a thermostaticelement. In such case, the lower end of the bellows 3|! may be directlyconnected to the valve needle 32.,

From the curve in Figure 2 it will be observed that different pressuresin pounds'per square inch absolute must be maintained in the vapor space28 for different temperatures in order to deliver a gas of constant B.t. u. value per cubic foot at atmospheric pressure. The pentane curveshows the total pressure required for any given temperature to givesaturation of air with pentane vapor at a composition of 13.5% pentaneand corresponding to approximately 550 B. t. u. per cubic foot ofmixture at atmospheric pressure. By adjusting and calibrating thebellows and bi-metallic hairpin,'my device can produce a gas mixture ofconstant B. t. 11. value for all temperatures. The hexane curve showsthe temperatures and pressures that must be maintained in order toproduce a gas mixture of constant B. t. u. value.'

It should be understood that my gas machine may be adapted to operate atany predetermined pressure for the prevailing temperature, therebyproducing gas mixtures with any predetermined heat value. For example,if the prevailing tem perature is 50 F., the pressure in pounds persquare inch absolute to be maintained within the carburetor may be aboveor below 43 pounds or square inch absolute, and if the pressure is above.43 pounds per square inch absolute, the B. t. u.

B. t. u. per cubic foot at atmospheric pressure.

Therefore it will be noted that I can" determine and control the B. t.11. value of the gas mixture discharged from the gas machine byregulating the partial pressure of air within the gas space above theliquid level of the carburant.

While I have described my invention with reference to specific examples,it is not intended that the invention shall be limited thereto except asincluded in the appended claims.

Under certain conditions it is desirable to use liquid fuels having arelatively wide boiling range chiefly because of their lower cost tomanufacture. When using fuels of this type and fuels havingsubstantially different boiling ranges and specific gravities, it isdesirable to compensate for differences in vapor pressure exerted byfuels of high and low gravity. It is also desirable to compensate forchanges in the vapor pressure of the fuel in the carburetor as the morevolatile constituents are evaporated therefrom.

In order to achieve this compensation I have made use of the fact thatthe vapor pressure of the fuel decreases with an increase in itsspecific gravity. A compensating mechanism which may be employed foroperating my gas machine under the conditions of 1 fluctuating fuelvolatility de-- through the sealed pivot 46. Lever arm 41' in turn isconnected to the needle valve member 32 by means of elastic tensionmember 48 which in this case is illustrated as a coil spring. The mannerof gravity compensation is as follows: When the specific gravity of thefuel in carburetor i3 increases, the float 45 is caused to rise and inturn reduces the tension on spring 48, thus permitting valve pin 32 toseat more readily and close ofi orifice 33. As a result the air pressureis permitted to act on diaphragm valve 26 and partially closed valve 23supplying air to carburetor 13, as previously described. The pressure ofthe air in the carburetor is thereby reduced,

thus tending to enrich the gas mixture contained in the vapor spacethereof, which is the desired compensation for the reduced volatility ofthe heavier fuel.

I claim:

1. An apparatus for carbureting air with volatile liquid hydrocarbons toproduce a gaseous fuel of constant heating value, which comprises aliquid hydrocarbon supply tank, means for passing air through thehydrocarbon contents of said tank, said tank having a gas space abovethe liquid level thereof for maintaining the carbureted air ata.pressure determined by the amount of air admitted to the tank, means formaintain- -ing a super-atmospheric pressure within said gas space, avalve for controlling the admission of air into the tank, and meansconnected to said first mentioned means and responsive to a decrease inthe specific gravity of the hydrocarbon fluid for regulating the valveto incream the amount of air passing therethrough.

2. The method of carburetting air with hydrocarbon gases to provide agas mixture whereinthe ratio between the air and the hydrocarbon gasesis a predetermined constant to provide a gas of uniform heating valuewhich comprises, contacting air directly with avolatile liquidhydrocarbon to carburet said air, maintaining. said carburetted air incontact with said liquid hydrocarbon under a super-atmospheric pressurepro-' ductive of said desired gas mixture ratio, varying the saidsuperatmospheric pressure by regulating the amount of air directlycontacting the liquid hydrocarbon to control the partial pressure of airwithin said mixture of air and gasified hydrocarbons in response tochanges in temperature of said liquid hydrocarbon, and delivering saidgas mixture at a lower pressure to a point of consumption.

3. The method of carburetting air with hydrocarbon gases to produce agas mixture wherein the ratio between the air and the hydrocarbon gasesis a predetermined constant to provide a gas of uniform heating valuewhich comprises, maintaining a volatile liquid hydrocarbon in acarburetor, passing air through said hydrocarbons and collecting the airand evolved hydrocarbon gases, maintaining the mixture of air andgaseous hydrocarbon under a super-atmospheric pressure productive ofsaid gas mixture ratio, and regulating the amount of air passing throughsaid liquid hydrocarbon to vary said super-atmospheric pressure of saidmixture of air and gasified hydrocarbons in response to changes in thetemperature of said liquid hydrocarbon.

4; The method of carburetting air with hydrocarbon gases to produce agasmixture wherein the ratio between the air and the hydrocarbon gases is apredetermined constant to provide a gas of uniform heating value whichcomprises, passing air under pressure through a volatile liquidhydrocarbon to carburet said air, maintaining the resultant gas mixturein contact with said hydrocarbon liquid at super-atmospheric 'prcssure,and increasing and decreasing said super-atmospheric pressure byincreasing and decreasing respectively the amount of air passed throughsaid liquid hydrocarbon in response to increases and decreasesrespectively of the temperature of said hydrocarbon liquid to maintainsaid desired gas mixture ratio.

5. The method of carburetting air with hydrocarbon gases to produce agas mixture wherein the ratio between the air and the hydrocarbon gasesis a predetermined constant to provide a gas of uniform heating valuewhich comprises, passing air under pressure through a volatile liquidhydrocarbon to carburet said air, maintaining the resultant gas mixturein contact with said hydrocarbon liquid at super-atmospheric pressure,and in increasing and decreasing said super-atmospheric,pressure byincreasing and decreasing respectively the amount of air passed throughsaid liquid hydrocarbon in response to increases and decreasesrespectively of the temperature of said hydrocarbon liquid and todecreases and increases respectively in the specific gravity of saidhydrocarbonliquid to maintain said desired gas mixture ratio. 7

6. The method of carburetting air with hydrocarbon gases to produce agas mixture wherein the ratio between the air and the hydrocarbon gasesis a predetermined constant to provide a gas of uniform heating valuewhich comprises, passing air under pressure through a volatile liquidhydrocarbon to carburet said air, maintaining the resultant gas mixturein contact with said hydrocarbon liquid at super-atmospheric pressure,and in increasing anddecreasing said super-atmospheric pressure byincreasing and decreasing respectively the amount of air passed throughsaid liquid hydro-carbon in response to decreases and increasesrespectively in the specific gravity of said hydrocarbon liquid tomaintain said desired gas mixture ratio.

'7. Apparatus for carburetting air with hydrocarbons to produce a gasmixture wherein the ratio between the air and the hydrocarbon gases is apredetermined constant which comprises, in combination, meansfor'passing air under pressure through a volatile liquid hydrocarbon tocarburet said air, means for confining resultant .gas mixture in contactwith said hydrocarbon liquid at super-atmospheric pressure, and meansconnected to said first mentioned means for increasing and decreasingsaid super-atmospheric pressure by increasing and decreasingrespectively the quantity of air passing through the liquid hydrocarbonin response to increases and decreases respectively of the temperatureof said hydrocarbon liquid to maintain said desired gas mixture ratio.

8. Apparatus for carburetting air with hydrocarbons to produce a gasmixture wherein the ratio between the air and the hydrocarbon gases is apredetermined constant which comprises, in combination, means forpassing air under pressure through a volatile liquid hydrocarbon tocarburet said air, means for confining resultant gas mixture in contactwith said hydrocarbon liquid at super-atmospheric pressure and meansconnected to said first mentioned means for increasing and decreasingsaid super-atmospheric pressure by increasing and decreasingrespectively the quantity. of air passing through the liquid hydrocarbonin response to increases and decreases respectively of the temperatureof said hydrocarbon liquid and to decreases and increases respectivelyin the specific gravity of said hydrocarbon liquid.

9. Apparatus for carburetting air with hydrocarbons to produce a gasmixture wherein the ratio between the air and. the hydrocarbon gases isa predetermined constant which comprises, in combination, means forpassing air under pressure through a volatile liquid hydrocarbon tocarburet said air, means for confining resultant gas mixture in contactwith said hydrocarbon liquid at super-atmospheric pressure and meansconnected to said first mentioned means for increasing and decreasingsaid super-atmospheric pressure by increasing and decreasingrespectively the quantity of air passing through the liquid hydrocarbonin response to decreases and. increases respectively in the specificgravity of said liquid.

10. In an air-gas carburetor wherein air under pressure is intimatelycontacted with a volatile liquid fuel in a closed chamber maintained atsuper-atmospheric pressure, the method of controlling the heating valueof the gas under changing fuel volatility, comprising varying the amountof air intimately contacted with said liquid fuel to regulate thepressure in said chamber in response to variations in the specificgravity of the liquid fuel therein.

11. An apparatus for converting volatile liquid hydrocarbons into agaseous fuel of constant lating the amount of air introduced directlyinto said liquid hydrocarbons and means responsive to the temperature ofsaid liquid hydrocarbons for modifying the operation of said pressureresponsive means.

12. An apparatus for carbureting air with volatile liquid hydrocarbonsto produce a gaseous fuel of substantially constant heating value, whichcomprises a liquid hydrocarbon supply tank, a carburetor, automaticmeans for maintaining a constant amount of liquid hydrocarbons in saidcarburetor, means providing a gas space above the liquid level in saidcarburetor, means for maintaining a superatmospheric pressure withinsaid gas space, means for introducing air directly into said liquidhydrocarbons, means connected to said means for introducing air andresponsive to the pressure of the gases within said gas space forregulating the amount of air introduced directly into said liquidhydrocarbons and means responsive to the temperature of said liquidhydrocarbons for modifying the operation of said lastnamed means.

13. An apparatus for gasiiying volatile liquid hydrocarbons to produce agaseous fuel of substantially constant heating value, which comprises acontainer partly filled with volatile liquid hydrocarbons, means formaintaining a superatmospheric pressure in the vapor space of saidchamber, means for introducing air directly into said liquidhydrocarbons, means connected to said means for introducing air andresponsive to the pressure within said chamber for regulating the amountof air introduced into said liquid hydrocarbons and means responsive totemperature changes of said liquid hydrocarbons and co-acting with saidpressure responsive means to modify the operation of said pressureresponsive regulating means, said temperature responsive means beingoperable to raise and lower the pressure limit of said pressureresponsive regulating means as the temperature in said container isincreased or decreased, respectively.

14. The method of carbureting air with vapors of volatile liquidhydrocarbons to provide an air-gas mixture of substantially constantheating value having a substantially uniform ratio of air tohydrocarbon, comprising maintaining a body of said liquid hydrocarbon,introducing air into intimate contact with said liquid hydrocarbon bodyat a superatmospheric pressure whereby all the air is completelysaturated with vapors of said hydrocarbon, collecting the resultingairgas mixture and controlling said super-atmospheric pressure byautomatically regulating the introduction of air in a manner to maintaina substantially constant ratio of air to hydrocarbon in said air-gasmixture under varying conditions of temperature of said liquidhydrocarbon.

15. The method of claim 14 wherein the introduction of air isautomatically regulated to maintain a substantially constant ratio ofair to hydrocarbon in said air-gas mixture under varying conditions oftemperature and specfic gravity of said liquid hydrocarbons.

HAROLD V. ATWELL.

